Adhesive or paint coating for toy articles

ABSTRACT

The invention is directed to resin coating, adhesive, and cement compositions comprising styrenic copolymers and a terpene solvent. The compositions are particulary useful for toy article applications because of the use of safe, naturally occuring terpene solvents. These compositions form high adhesion bonding with molded elastomeric styrene copolymer surface substrates. The invention is also directed to a method of applying the instant coatings to substrate surfaces.

This application is a Divisional Application of prior U.S. applicationSer. No. 09/729,071 filed on Dec. 4, 2000 now U.S. Pat. No. 6,503,569.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a novel composition and process forapplying a styrenic based adhesive, cement, coating, or paint tothermoplastic polymer surfaces, particularly to toy articles formed ofelastomeric materials. Because the coating composition uses naturallyoccurring terpene solvents, it is safe for use as a coating or paint fortoy articles which can be safely used by children.

BACKGROUND OF THE INVENTION

Children's toys and dolls, in particular, have a history dating backinto antiquity. Generally, the technology surrounding the manufacture ofdolls centers on creation of an attractive doll face, miniturizedapplication of conventional clothes, manufacture of a doll body usingplush or other sculptural techniques, and the simulation of the hairwith sculptural elements, fibers, or other techniques. In the case ofdoll faces, the doll maker has a wide panoply of possible constructionsand manufacturing techniques at his disposal. Traditional techniquesinvolve the use of plaster-like or hard plastics material to cast a dollface. In time, however, soft rubber materials such as styrene-butadienerubber (SBR) and styrene-butadiene-styrene block copolymer (Kraton)elastomers have come to replace plaster and hard plastics in theproduction of doll heads because of their realistic look and feel.

The soft rubber doll faces include all the normal features of a humanfigure simulated by the doll including the entire head, including wellformed lips, teeth, cheeks, nose, chin, ears, and forehead. After theinjection molding of an elastomeric doll face, it is finished byapplying a dye or other similar material to give the face a natural skincolor. Parts of the facial skin are often given a contrasting reddishcolor to improve the attractiveness of the face, as by using an airbrush may be used to apply a patch of rosy hue to the cheeks.

Regardless of the type of paint used on a toy doll article, it hasremained imperative that such materials be safe for young children.Safety requirements have evolved through the years as safety concernshave grown. Generally, safety requirements mandate that any materialcompositions used in a toy be odorless, nonirritating to the skin oreyes or the like, and be nontoxic if ingested. Additional requirementshave been expected of materials used to coat or paint toy articles inthat they must be non-peeling, requiring that the coating or painttenaciously adhere to the toy item to avoid flaking or peeling andpossible consumption by a child user. Accordingly, such paints should beresistant to oxidation and flaking, particularly as applied toelastomeric rubber surfaces of soft doll faces. And further the paintshould be able to withstand the stretching and other physical abuse of achild so that the appearance of the painted surface is maintained. Andabove all the paint or coating composition must avoid the use ofundesirable volatile organic solvents the residual presence of which canbe dangerous due to the toxic effect of certain aromatic and chlorinatedhydrocarbon solvents.

In view of the environmental, health and safety concerns in the use oforganic solvents, less controversial solvents such as water or mineralspirits have been used to provide toy paint or coating compositions. Themineral spirits is less toxic and considered generally safe in coatingapplications for toys and, of course, water is completely safe and nonodiferous as a coating solvent for any coating applications. Howeverboth solvents evaporate relatively slowly over a long period of timewhich detracts from the overall effectiveness of these coatingcompositions. For example, when applying a water based latex emulsionpaint to a soft elastomeric item, a slower evaporation time delays setup of the paint coating composition and inhibits complete bondingbetween the joined surfaces of the applied coat and the article. As aresult of an extended drying period, non-uniform and unstable coatingsresult leaving these coating vulnerable to use factors which generatepeeling and splitting among other negative consequnces.

As indicated above, the class of the styrenic elastomeric materialscommonly used to mold doll faces and other toy articles are A-B-A typeblock polymers such as styrene-butadiene-butylene copolymer-styrene orstyrene-butadiene-styrene, manufactured by Shell and sold under thetrademark Kraton. The molded polymeric doll faces tend to be dull andunattractive and so are finished by application of a skin coating orpaint to provide a good facial appearance to this facial piece. It hasnow been found that an elastomeric adhesive coating comprising a styrenebased resin and a terpene solvent has particular advantages in formingtenaciously bonded adhesive coatings on styrenic resin molded items.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a resincoating composition particulary useful for toy article applicationscomprising a styrenic copolymer and a terpene solvent. The terpenes arenaturally occuring, biodegradable compounds characterized by a very lowlevel release of organic vapor and, accordingly, they are consideredsafe as solvents for coating or paint applications for toy items. Theterpene solvents have also been found particularly effective insolubilizing styrenic copolymers and enhancing the bonding of thecopolymers to form adhesive coatings on resinous substrate surfaces.Therefore compositions made in accordance with the present invention arecompletely non-toxic, environmentally and child safe, and result in anoverall superior coating or paint product.

Of particular significance, styrenic copolymer/terpene coatingcompositions made in accordance with the present invention preliminarilydry in a rapid manner to provide a strong bond with polymeric substratesurfaces thereby engendering consequent use durability to the appliedcoat or film. The terpene solvent has been found capable of completelysolubilizing styrene based resins, styrenic copolymers, pigments orother additives to provide a coating composition having a relativelyhigh solids content up to 20% by weight of the total composition.Therefore while the resinous coating compositions made in accordancewith the present invention can be viscous, they can be formulated to bepoured and applied by hand, brush or other manipulative means foruniform coating application at ambient temperatures, while comprising asufficient percentage of solids to avoid shrinkage following evaporationof the solvent.

The discovery of the present invention is that one may formulate asuperior adhesive, cement, coating or paint composition by combining astyrenic copolymer and a terpene solvent in certain amounts to form acoating composition of completely unexpected character when applied toelastomeric substrate surfaces. While the coating composition iseffective with any thermoplastic resin surface, the instant compositionsare especially effective as a coating or adhesive for styrene basedelastomers, those copolymers with a linear A-B-A configuration in whichA is a polystyrene endblock. It is believed that the terpene solvent isparticularly effective in solubilizing the styrene-based copolymermolecules of the substrate surface thereby takifying the elastomericsurface to generate a miscible interface with the applied coat resultingin an amalgam like bonding upon drying. The terpene solvent has beenparticularly effective with styrene based elastomeric copolymer surfaceshaving unsaturated block segments such asstyrene-ethylene-butylene-styrene (SEBS) surfaces. Consequently theresulting coating is characterized by an exceptional durability,elongation and flexibility. Because the coating compositon employscertain naturally occuring terpene solvents, they are safe for use aspaints for children's toys and are particularly useful in applicationsto the soft elastomeric materials used in doll facial structures wherethe paint coatings are expected to withstand the rigorous and hostileenvironment of child use.

The present invention is more particularly directed to a protective oradhesive coating for elastomeric substrates comprising from about 0.1%to 20% by weight of a styrenic copolymer resin and from 80% up to 99.9weight % of a terpene solvent. A preferred protective or ornamentalpaint coating composition comprises from about 0.5% to 5% of a styrenicresin selected from the group of styrene butadiene rubber (SBR),styrene-butadiene-styrene (S-B-S), and styrene-ethylene-butylene styreneSEBS elastomeric block copolymers and from 95 to 99.5 wt. % of a terpenesolvent. The preferred terpene solvents in the instant coatingcompositions include a monoterpene or sesquiterpene. This coatingcomposition is found very effective in application to styrenic surfacesubtrates and particularly, styrene-ethylene-butylene-styreneelastomeric copolymer surfaces. An application of the subject protectiveor adhesive coating include the steps of (i) providing an elastomericresin substrate; (ii) applying a composition comprising from about 0.1%to 20.0% by weight of a styrenic copolymer resin and from 80.0% to 99.9wt. % of a terpene solvent to the elastomeric substrate; and (iii)curing the applied composition to form a layer on the elastomericsubstrate.

In yet another embodiment, the instant composition can be formulated asan adhsive or cement to act as a glue when applied to a styrenicelastomeric substrate. A cement, glue, or adhesive compositon comprisesfrom about 5% to 10.0 wt % of the styrenic resin and from 90% to 95 wt %of the terpene solvent. The application of this glue composition includethe steps of (i) providing an elastomeric resin substrate surface; (ii)contacting the surface with an effective amount of a compositioncomprising from about 5% to 10.0% by weight of a styrenic copolymerresin and from 90.0 to 95 wt. % of a terpene solvent; and (iii) curingthe applied composition to form an adhesive layer on the elastomericsubstrate. Any curing steps in the application of the coatingcompositions include any means (e.g. heating) for evaporating theterpene solvent or otherwise hardening an applied coating or film of theinstant formulation to form a hardened or solid layer on a substratesurface.

The coatings and adhesive compositions herein are characterized byviscosities approaching that of ordinary paint or the more viscous glueformulations. A dried coat of the instant formulations have elongationvalues and adhesion characteristics conforming to the quality and safetystandards necessary for application to toy products. In addition, thesecoatings or adhesives have ultimate tensile values of greater than about500 psi indicating that toughness is not being sacrificed toflexibility. It is important that coatings or adhesives used forapplication to toy articles, such as a soft elastomeric doll facialelement, have high tensile strength so that the coated or paintedarticle have child use durability especially as to stretchability. Theinstant coating and adhesive compositions have flexibility at bothambient and cold temperatures.

Paint application equipment constrains good application of coatings withviscosities that are greater than average paint and surface coatingformulations and accordingly the viscosity of the instant compositionsfor a paint or film coating application have to be controlled by keepinga proper ratio of styrenic resin to terpene solvent. Stringing, nozzleclogging, and inconsistent or poor coating application occurs at highviscosities. A combination of high percent elongation, high adhesion,and low modulus in the instant compositions are shown to have goodcorrelation with excellent lay flat characteristics in a finish coatedelastomeric article. The resultant properties of the instant coating andadhesive compositions make them ideally suited for toy paintapplications especially where good lay flat character is required.

DETAILED DESCRIPTION OF THE INVENTION

The present composition is the combination of two key ingredients, thestyrene based copolymer and the terpene solvent, which synergisticallyprovide for the desirable properties of the instant invention recitedabove. The instant styrenic based coating composition is characterizedby the presence of a terpene solvent that is capable of solubilizingresinous components, particularly styrenic copolymers, to provide auniform composition for application to elastomeric at ambienttemperatures. Terpene compounds that are suitable for this purposeinclude but are not limited to monoterpenes and sesquiterpene; themonoterpenes include pinashe, both the alpha and beta isomers; gammaterpinene; delta-3-carene; limonene, both the l and d isomers;methadiene; and dipentene (the racemic mixture of the isomers ofoptically active limonene). A sesquiterpene compound used in the presentinvention is the general name for the compound having the formulaC₁₅H₂₄. Examples of the sesquiterpene compound include cadinenes,caryophyllene, copaene, alpha-farnesene, humulene, longifolene,thujopsene and ylangene.

Preferred monoterpene and sesquiterpene solvents include d-limonene,l-limonene, dl-limonene, dipentene, terpineol, sesquiterpene, naturalextracts such as lemon oil and orange oil containing the above-mentionedterpenes or mixtures thereof. Limonene is a natural product found invarious ethereal oils such as oils of lemon, orange, caraway, dill andbergamot and which possesses a citrus-like odor and is found incommercial quantities in citrus fruits. Dipentene is found in largequantities in pine trees and has a distinct pine scent. Among all thelisted terpenes, limonene in all forms is preferably used because it hasa pleasant mild citrus scent, is color free and is found to enhance thecoloring of paint coatings. Optimum coating composition results havebeen achieved with the isomer d-limonene. Terpene solvents in thepractice of the present invention are available commercially fromArizona Chemical Company of Panama City, Fla. under the trademarkACINTENE “LS” series. The terpene may be combined or blended with othersafe solvents, such as mineral spirits, to lower the overall solventemmision or scent character of the composition and to facilitate earlyset up or curing following application of the coating or adhesivecomposition. Additionally, any other additive may be used to render theparticular terpene satisfactory for use in a particular application. Forexample, deoderizing or perfuming agents can be used to temper the scentof odiferous terpenes such as pine scented dipentene and render theterpene as usable for toy coating application.

The total amount of solvent provided in the subject coating and adhesivecompositions will vary depending on the character of the compositionprepared, but will generally range from about 80.0% to 99.9 wt %, butpreferably from about 90 to 99 wt % in the case of an adhesive orcoating application contemplated herein. For application of a lay flatcoating the terpene solvent is preferably present in an amount of from95% to 99% by weight and as an adhesive or cement application thesolvent is present in amounts of from 90.0% to 95% by weight of thetotal composition. The remainder of the composition comprises a styrenicresinous component in amounts ranging form about 0.1% to 20.0% by weightand preferably ranging from about 1% to 10.0% by weight of the totalstyrenic resin/terpene solvent composition. As indicated above, optionalfillers, gellants, surfactants, pigments, dyes, perfuming agents andother additives may be included.

The resinous component of the present composition is a styrene basedthermoplastic elastomer which include blends prepared by thecopolymerization of one or more conjugated dienes, such as butadiene,isoprene, and chloroprene with styrene. Useful blends in the preparationof the instant coating and adhesive compositions include styrenebutadiene rubber (SBR) and styrene-butadiene-styrene block copolymer.Styrene-based thermoplastic elastomers comprise blocks of hard segments,e.g., polystyrene, and blocks of soft segments, e.g., polyisoprene,polybutadiene, poly(ethylene-propylene), poly(ethylene-butylene), andpolypropylene. Thus, useful styrene-based elastomers may comprise, forexample, blocks of polystyrene and blocks of polyisoprene, or blocks ofpolystyrene and blocks of polybutadiene, of blocks of polystyrene andblocks of poly(ethylene-butylene). Examples of styrene basedthermoelastic elastomers useful in the present composition, includestyrene-ethylene-butylene-styrene block coplymers (e.g. KRATON G-1650,G-1651, G-1652, and G-1657) and styrene-ethylene-propylene blockcopolymers (e.g. KRATON G-1701, G-1702 and G-1762X), all commerciallyavailable from Shell Chemical Company. Combinations of these blockcopolymers can also be included. Styrene-ethylene-butylene-styrene(SEBS) copolymers are particularly effective because they have superiorphysical properties manifested in the coatings of the present invention,including durability in that it can withstand prolonged wear and tear inthe form of impact resistence and flexibility. Again, the amount ofthermoplastic elastomer useful in the present coating and adhesivecompositions to achieve the desired characteristics is from about 0.1%to 20 wt % based on the total weight of the styrenic copolymer/terpenesolvent composition. The compositional weights recited herein are basedon the resin/solvent composition and inclusion of any additives willaccordingly affect the overall compositional weight but the ratio ofstyrenic resin to terpene solvent will remain the same as initiallyformulated; that is, a 5% by weight styrenic resin in 95 wt % d-limonenewill remain in the same ration to one another even with the addition ofdye or pigment.

It is to be emphasized that the purview of the compositional inventionherein is the combination of a styrene based thermoplastic polymer and aterpene solvent in certain amounts for adhesion or paint application toelastomeric substrate surfaces. As indicated above, especially effectiveelastomers are styrene-ethylene-butylene-styrene (SEBS) copolymers whichare solvated very effectively with a terpene such as d-limonene, thecompatibility between the polymer and terpene solvent being speculatedas being due to the mutual unsaturation in the terpene and theethylene-butylene segment of the styrenic polymer. The particularcompatibility of the terpene and and the SEBS polymer in the coatingcomposition follows on through application to a solid molded orotherwise formed SEBS substrate surface, which acts as an optimalsubstrate surface for application of the SEBS/terpene (d-limonene)adhesive or paint coating composition. Accordingly, the most preferredembodiment of this invention is an application of an SEBS/terpenecoating to a solid molded SEBS substrate surface.

The instant coating may be applied as a paint and accordingly thecomposition would contain a pigment, dye, or colorant in amounts of upto 3% by weight in addition to the thermoplastic elastomeric resin andterpene solvent. The pigment used herein is not particularly limited andvarious inorganic or organic pigments can be employed. Concrete examplesof pigments and colorants are: synthetic organic colorants sold as theT-series by the Day Glow Corporation of South Gate City, Calif. Otherpigments which can be used include sodium aluminum sulpho silicate soldas MR 582 by the Cleveland Pigment Corp. of Cleveland, Ohio; polyamidecondensates with organic dyes with less than 2% phthalocyanine; andtetra-chloro-zincate sold by the Day Glow Corporation.

In reinforcement of the additives mentioned above, compositions made inaccordance with the present invention may additionally employ gellingand thickening agents such as ethylene glycol and clay mixtures toprovide the desired texture and body for ease of application of theinstant coating compositions. In certain coating applications, fillersand stabilizers such as organic and inorganic fibers, sand, talc andmixtures thereof may also be included as part of the coatingcomposition. Compositions of the present invention can be applied by anymeans such as with a brush, a cloth, or a spray applicator. The surfaceof a polymeric substrate surface should be clean and dry beforeapplication of the instant coating. Once applied the compositions shouldbe allowed a period of at least 30 minutes to allow curing of thecomposition by drying of the terpene solvent.

Having generally described the present invention, the following examplesare set for the below to further demonstrate compositions embodying thepresent invention. The compositions of the present invention areprepared by adding the specified amount of styrenic resin to the statedamount of terpene solvent under agitaiton. Specified amounts of otheringredients are added where indicated. In the following Example 1, theapplied paint composition is subjected to an Eraser Abrasion Test, aSurface Coating Adhesion (Tape Pull) Test, and Stretch Tests todetermine the adhesion and stretch characteristics of the presentstyrenic copolymer/terpene coating composition. These tests are carriedout employing standard Quality and Safety Operating Procedures of theAssignee of the present application, Mattel, Inc.

EXAMPLE 1

4 percent by weight of a styrene-ethylene-butylene-styrene (SEBS)copolymer elatomer known as Kraton 1651 is dissolved in a 96 percent byweight of the terpene d-Limonene in a flask. After complete disolutionof the styrenic elastomer the viscosity of the solution being slighlygreater than water. 1% by weight of a red pigment was added to the paintcoating solution with stirring continued until dispersion of the pigmentand generation of a red color to the coating (paint) composition. Amolded soft elastomeric doll face comprised of a solid molded SEBSelastomeric copolymer was provided and the paint composition applied tothe cheek and lip areas of the molded doll face. The rubbery painteddoll facial item was allowed to dry for one hour. Thereafter the softpainted rubbery painted doll face was subjected to 1600% Elongation Testand an Eraser Abrasion Test. The tests revealed that the paint coatingdid not split, peel, or abrade under the tests. The surface bondingbetween the applied coating and the surface substrate was so strong anduniform so as cause complete adhesion between the styrenic coating andthe rubbery elastomeric substrate surface.

EXAMPLE 2

95 percent by weight of the same styrenic thermoplastic elastomer ofExample 1 (Kraton 1651) was dissolved in a 4 percent by weight volume ofthe terpene d-Limonene in a wide mouth beaker. After complete disolutionof the styrenic thermoplastic elastomer with difficult stirring theviscosity of the solution was approximate that of a thick glue.Thereafter a rubbery styrenic copolymer substrate surface is providedand a dab of the viscous elastomeric terpene solution is applied to therubber surface and as separate piece of rubbery material patched ontothe dabbed viscous area. After drying for an hour the patched rubberitem was found glued tenaciously to the thermoplastic elastomericsubstrate surface. Attempts at removal of the patch results in damage tothe elastomeric substrate surface.

The adhesive and coating compositions of the present invention possessunique combinations of properties, including both a high degree ofelastic durability under suddenly applied stresses, and a high degree ofplasticity when the stress is applied more slowly. The misciblecharacter of the styrenic polymer/terpene composition when applied to amolded polystyrene endblocked polymer substrate surface causes an anneallike bonding with that substrate surface so as to form a physicallyindistinguishable layer with that surface. Accordingly the well bondedcompositional layer reacts to the physical stresses applied to the bodyof the substrate in exactly the same manner as the underlying substrate.Therefore the coating will stretch, strain, and impact as its substrateunderlayer and shoe no splitting or peeling. Other properties includeexcellent stability throughout a very wide temperature range. Mostimportantly, the applied coatings of these novel compositions arenontoxic and, therefore, coated toy items are safe for use by childrenof all ages.

Having thus described the principals of the invention, together withillustrative embodiments thereof, it is to be understood that althoughspecific terms are employed, they are used in a generic and descriptivesense and not for the purpose of limitation, the scope of the inventionbeing set forth in the following claims.

What is claimed:
 1. A coating composition for thermoplastic resinsubstrate surfaces comprising from about 0.5% to 5% by weight of astyrenic copolymer resin and from 95% to 99.5% by weight of a terpenesolvent, wherein the terpene solvent is selected from the groupconsisting of d-limonene, 1 limonene, dl-limonene, dipentene, terpineol,sesquiterpene, natural extracts containing these terpenes, and mixturesthereof, and the styrenic copolymer resin is selected from the groupconsisting of styrene-butadiene rubber, styrene-butadiene-styrene blockcopolymers, styrene-ethylene-propylene-styrene block copolymers,styrene-ethylene-butylene-styrene block copolymers and mixtures thereof.2. The coating composition of claim 1, (wherein the styrenic copolymerresin is a styrene-ethylene-butylene-styrene block copolymer.
 3. Thecoating composition of claim 1 wherein the terpene solvent isd-limonene.
 4. A coating composition for thermoplastic resin substratesurfaces comprising from about 5.0% to 10% by weight of a styreniccopolymer resin and from 90% to 95% by weight of a terpene solvent,wherein the terpene solvent is selected from the group consisting ofd-limonene, 1 limonene, dl-limonene, dipentene, terpineol,sesquiterpene, natural extracts containing these terpenes, and mixturesthereof, and the styrenic copolymer resin is selected from the groupconsisting of styrene-butadiene rubber, styrene-butadiene-styrene blockcopolymers, styrene-ethylene-propylene-styrene block copolymers,styrene-ethylene-butylene-styrene block copolymers and mixtures thereof.5. The coating composition of claim 4 wherein the styrenic copolymerresin in the coating composition is a styrene-ethylene-butylene-styreneblock copolymer.
 6. The coating composition of claim 4 wherein theterpene solvent is d-limonene.